Billiard cue shaft for reducing deflection

ABSTRACT

A billiard cue shaft includes a shaft body having first and second ends, a longitudinal axis and a first length. The shaft body includes a wooden rod and an outer layer of fiber reinforced plastic (FRP) wrapped around the surface of the wooden rod. The shaft body further includes a straight section with a first outer diameter and a second length, and a tapered section. The wooden rod has a bore with a predetermined inner diameter and a predetermined depth. The predetermined depth of the bore of the wooden rod is about 15% to 55% of the first length of the shaft body. The predetermined inner diameter of the bore of the wooden rod is about 51% to 81% of the first outer diameter of the straight section of the shaft body. The billiard cue shaft thereby has the advantage of natural wood and can decrease the deflection.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates generally to a billiard cue, and more particularly to a billiard cue shaft for reducing the degree of deflection.

2. Description of the Related Art

It is well known that a conventional billiard cue is basically comprised of a shaft, a butt connected to one end of the shaft by a joint and a ferrule mounted on an opposite end which supports a tip. Typically, the shaft of the conventional billiard cue is most made of hard wood, such as hard maple or ash, for its moderate weight and flexibility. However, such wooden shafts have several drawbacks, for example, its body is liable to warp under moist environments, its surface is likely to be dented when being collided with something hard, its flexibility cannot be adjusted, etc. As a result, the accuracy of hitting is decreased.

U.S. Pat. No. 5,725,437 discloses a shaft of a billiard/pool cue with a ferrule mounted on the tip end thereof. The ferrule is made of a material having greater compression than the compression of the material forming the shaft to absorb a portion of the impact forces. The shaft further has a hollow bore formed in the tip end of the shaft to reduce the weight of the tip end. Such designs result in less deflection of the ball from the longitudinal stroke axis of the shaft. However, it is found that the compression of the ferrule is not easy to control in manufacturing. In addition, there is no teaching or suggestion in this patent that what is the preferable size of the diameter and depth of the bore to get an appropriate weight of the tip end of the shaft. Furthermore, the improved shaft still cannot overcome the problems of warpage when being exposed to moist environments and of being likely to be dented when colliding with something hard.

It has also been proposed in U.S. Pat. No. 6,110,051 to provide a billiard cue shaft formed of composite material consisting of fibers in a binder. In this patent, the shaft has a hollow bore disposed on the tip end thereof to form an outer wall in the tip end with a thickness between about 0.03 and 0.05 inches. Such designs are combined to decrease the mass of the tip end of the shaft while maintaining substantially all of the stiffness of a conventional shaft formed of a hard maple to minimize buckling of the tip end of the shaft and thereby substantially decrease deflection of the cue ball from its intended path of movement along a path parallel to the stroke axis of the shaft. However, the most significant disadvantage is that the performance of the billiard cue shaft disclosed in the patent in absorbing the impact force when hitting a ball is much worse than that of the conventional billiard cue made of natural wood materials.

Therefore, an improved shaft for a billiard cue that has the advantage of natural wood, does not warp under moist environments, does not dent when being collided with something hard, and can decrease the deflection needs to be developed.

Accordingly, an object of the present invention is to provide a billiard cue shaft that has the advantages of natural wood but the body thereof will not warp under moist environments and will not dent when being collided with something hard.

Another object of the present invention is to provide a billiard cue shaft that allows the user to operate the billiard cue stably when hitting a cue ball.

Still another object of the present invention is to provide a billiard cue shaft that allows the user to hit a cue ball with high accuracy.

Still another object of the present invention is to provide a billiard cue shaft that effectively decrease the deflection of a cue ball by significantly controlling the flexibility of the front section of the shaft within an appropriate range while maintaining the weight and stiffness thereof equal to or not be worse than that of a comparable shaft made of wooden materials.

SUMMARY OF THE INVENTION

Thus, in a preferred embodiment, the billiard cue shaft comprises a shaft body having a first end, a second end, a longitudinal axis and a first length extending from the first end along the longitudinal axis to the second end. The shaft body includes a wooden rod and an outer layer of fiber reinforced plastic (FRP) wrapped around the surface of the wooden rod. The shaft body further includes a straight section having a first outer diameter and a second length extending from the first end of the shaft body toward the second end of the shaft body, and a tapered section, whose outer diameter continues to increase from an end of the straight section to the second end of the shaft body, extending from the end of the straight section to the second end of the shaft body. The wooden rod includes a bore with a predetermined inner diameter and a predetermined depth. The predetermined depth of the bore of the wooden rod extends from the first end of the shaft body along the longitudinal axis to the second end of the shaft body and is about 15% to 55% of the first length of the shaft body. The predetermined inner diameter of the bore of the wooden rod is about 51% to 81% of the first outer diameter of the straight section of the shaft body.

The wooden rod of the shaft body is, for example, made of hard maple or ash. Further, the outer layer is, for example, formed of fiberglass impregnated with epoxy resin. The thickness of the outer layer is preferably about 3.6% to 5.8% of the first outer diameter of the straight section of the shaft body. More preferably, the thickness of the outer layer is about 0.74 mm.

The predetermined depth of the bore of the wooden rod is preferably equal to or less than the second length of the straight section of the shaft body such that the front portion of the shaft body has a constant flexibility. The second length of the straight section of the shaft body is preferably about 31% to 54% of the first length of the shaft body.

The first length of the shaft body is about 711 mm to 813 mm. Preferably, the first length of the shaft body is about 737 mm, the second length of the straight section of the shaft body is about 394 mm and the predetermined depth of the bore of the wooden rod is about 370 mm.

The first outer diameter of the straight section of the shaft body is about 10.5 mm to 13.5 mm. Preferably, the first outer diameter of the straight section of the shaft body is about 12.75 mm. The predetermined inner diameter of the bore of the wooden rod is about 5.36 mm to 10.94 mm. Preferably, the predetermined inner diameter of the bore of the wooden rod is about 8.50 mm.

In the present invention, the weight of the shaft is kept at about 96 grams to 120 grams, preferably, at about 106 grams.

More clearly speaking, firstly, the billiard cue shaft of the present invention is constructed to provide appropriate flexibility and to significantly reduce mass at the front section thereof such that the cue ball can follow a path of movement that is as parallel as possible to the intended line of stroke of the billiard cue. The appropriate flexibility and significantly reduced mass are achieved by forming a straight section with a predetermined outer diameter and a predetermined length, and a bore with a predetermined inner diameter and a predetermined depth. Secondly, the billiard cue shaft of the present invention is constructed to have a straight section with a predetermined length extending from the first end to enable the billiard cue shaft being operated stably by a user when the straight section of the shaft body is rested on a bridge formed with one hand of the user. Thirdly, the billiard cue shaft of the present invention is constructed to have an outer layer of fiber reinforced plastic (FRP) wrapped around the surface of the wooden rod such that the shaft body of the billiard cue shaft will not warp under moist environments and will not dent when being collided with something hard.

BRIEF DESCRIPTION OF THE DRAWINGS

The various features, advantages and other uses of the present invention will become more apparent by referring to the following detailed description and drawing in which:

FIG. 1 is a side view of a billiard cue with a shaft embodied according to the present invention;

FIG. 2 is a cross sectional view of a shaft body of the shaft taken along line 2-2 in FIG. 1;

FIG. 3 is a cross sectional view taken along line 3-3 in FIG. 2;

FIG. 4 is a cross sectional view taken along line 4-4 in FIG. 2;

FIG. 5 is a schematic drawing showing a testing for measuring the flexibility of the billiard cue shaft shown in FIG. 1; and

FIGS. 6 and 7 are vector diagrams depicting the impact of a conventional cue shaft and the cue shaft of the present invention with a cue ball.

DETAILED DESCRIPTION OF THE INVENTION

Referring firstly FIGS. 1-4, there is shown a billiard cue 100 with a shaft 10 constructed in accordance with the teachings of the present invention. The billiard cue 100 includes a shaft 10 and a butt 12 connected to the shaft 10 by a connector 13. The shaft 10 has a top end on which a ferrule 14 and a tip 15 are mounted. The butt 12 has a bottom end on which a rear pad 16 is mounted.

The billiard cue shaft 10 comprises a shaft body 20 having a first end 22, a second end 24, a longitudinal axis X-X′ and a first length L₁ extending from the first end 22 along the longitudinal axis X-X′ to the second end 24. The first length L₁ of the shaft body 20 is exemplary about 711 mm to 813 mm. Preferably, the first length L₁ is about 737 mm.

According to the present invention, the shaft body 20 is constructed to have a straight section 26 and a tapered section 28. The straight section mentioned here means that it has a constant outer diameter. In more detail, the straight section 26 has, as shown in FIGS. 2 and 3, a first outer diameter D₁ and extends from the first end 22 to the line a-a′ by a second length L₂. The tapered section 28 extends from the line a-a′ to the second end 24 with an outer diameter continuously increasing from the line a-a′ to the second end 24. Preferably, the second length L₂ of the straight section 26 is about 31% to 54% of the first length L₁. Preferably, the second length L₂ of the straight section 26 is about 394 mm. The first outer diameter D₁ of the straight section 26 is exemplary about 10.5 mm to 13.5 mm. Preferably, the first outer diameter D₁ of the straight section 26 is about 12.75 mm.

The shaft body 20 includes a wooden rod 30 usually made of hard maple or ash and an outer layer 40 of fiber reinforced plastic (FRP) wrapped around the surface of the wooden rod 30.

In the present invention, the wooden rod 30 further includes a bore 32 having an inner diameter D₂ and a depth H₁ extending from the first end 22 along the longitudinal axis X-X′ to the second end 24. The depth H₁ and the inner diameter D₂ should be properly matched with each other so that the front portion of the shaft body 20 has appropriate flexibility and significantly reduced mass. The depth H₁ of the bore 32 of the wooden rod 20 is preferably about 15% to 55% of the first length L₁ of the shaft body 20. More preferably, the depth H₁ of the bore 32 of the wooden rod 30 is about 370 mm. It is noted that the depth H₁ of the bore 32 preferably is equal to or less than the second length L₂ of the shaft body 20 such that the front portion of the shaft body 20 has a constant flexibility. The inner diameter D₂ of the bore 32 of the wooden rod 30 is about 51% to 81%, preferably 51% to 70%, of the first outer diameter D₁ of the straight section 26 of the shaft body 20. The inner diameter D₂ of the bore 32 is exemplary about 5.36 mm to 10.94 mm. Preferably, the inner diameter D₂ of the bore 32 is about 8.50 mm.

In addition, in the present invention, the outer layer 40 is completely wrapped around the surface of the wooden rod 30. The outer layer 40 is formed of fiber reinforced plastic (FRP), for example, fiberglass impregnated with epoxy resin, and has a predetermined thickness T₁. The thickness T₁ of the outer layer 40 is preferably about 3.6% to 5.8% of the first outer diameter D₁ of the straight section 26 of the shaft body 20. More preferably, the thickness T₁ of the outer layer 40 is about 0.74 mm. It must be mentioned that the weight of the billiard cue shaft 10 can be controlled in a certain value for having the specific size of the shaft body 20. The weight of the billiard cue shaft 10 is generally kept at about 96 grams to 120 grams, preferably, at about 106 grams.

The advantages of the billiard cue shaft 10 of the present invention may be more clearly understood by reference to FIGS. 5-7. FIG. 5 shows a testing for measuring the flexibility of a billiard cue shaft. Firstly, the first end of a tested billiard cue shaft is placed on a first support device S₁ of a supporting means S and the second end of the tested billiard cue shaft is placed on a second support S₂ of the supporting means S. The distance herein between support S₁ and support S₂ is 500 mm. Then, a pressure means M applies a pressure of 22 pounds (lb) at a speed of 10 mm/min to the pressure point P of the tested billiard cue shaft for getting a bending amount of the tested billiard cue shaft at point P. The bending amount of a prior art cue shaft 80 without a bore is 0.313 inches. The bending amount of a billiard cue shaft of the present invention with a straight section of 394 mm length, and a bore of 280 mm depth and of 8.50 mm inner diameter is 0.338 inches. The bending amount of a billiard cue shaft of the present invention with a straight section of 394 mm length and a bore of 370 mm depth and of 8.50 mm inner diameter is 0.361 inches.

The performance of a prior art cue shaft and the billiard cue shaft provided by the present invention when hitting a cue ball off center is shown in FIGS. 6 and 7. Firstly, referring to FIG. 6, when hitting a cue ball 90 with a prior art cue shaft 80, if the hitting point 82 is off the center 92 of the cue ball 90 by a distance d, a deflection usually occurs. In more detail, when being lined up with an intended path P₀ of movement of the cue ball to strike the hitting point 82 of the cue ball 90, the prior art cue shaft 80 would apply a side force F₀ to the cue ball 90. The side force F₀ is a resultant of a vertical component force F₀₁ and a horizontal component force F₀₂. Due to the effect of the horizontal component force F₀₂, the actual path P₁ of the cue ball 80 will deflect from the intended path P₀ by an angle θ₀.

Referring now to FIG. 7, when being lined up with the intended path P0 of movement of the cue ball 90 to strike the hitting point 82, the billiard cue shaft 10 provided by the present invention would also apply a side force F₀ to the cue ball 90. However, because the front section of the billiard cue shaft 10 has appropriate flexibility and significantly reduced mass, especially in the straight section 26, will produce an allowable buckling, as shown by the dotted line in FIG. 7. The allowable buckling will apply another side force Fr on the cue ball 90. This side force F_(r) is a resultant of a vertical component force F_(r1) and a horizontal component force F_(r2). As shown in FIG. 7, the horizontal component force F_(r2) can just offset the horizontal component force F₀₂. Therefore, the actual path P₂ of the cue ball 90 will deflect from the intended path P₀ by an angle θ₁ being less than θ₀. 

What is claimed is:
 1. A billiard cue shaft comprising: a shaft body having a first end, a second end, a longitudinal axis and a first length extending from the first end along the longitudinal axis to the second end; the shaft body including a wooden rod and an outer layer of fiber reinforced plastic (FRP) wrapped around the surface of the wooden rod; the shaft body further including a straight section with a first outer diameter and a second length extending from the first end thereof toward the second end, and a tapered section extending from an end of the straight section to the second end of the shaft body; the wooden rod having a bore with a predetermined inner diameter and a predetermined depth extending from the first end along the longitudinal axis to the second end; the predetermined depth of the bore of the wooden rod being about 15% to 55% of the first length of the shaft body; and the predetermined inner diameter of the bore of the wooden rod being about 51% to 81% of the first outer diameter of the straight section of the shaft body.
 2. The billiard cue shaft of claim 1, wherein the outer layer comprises fiberglass impregnated with epoxy resin.
 3. The billiard cue shaft of claim 1, wherein the predetermined depth of the bore is equal to or less than the second length of the straight section of the shaft body.
 4. The billiard cue shaft of claim 1, wherein the second length of the straight section of the shaft body is about 31% to 54% of the first length of the shaft body.
 5. The billiard cue shaft of claim 4, wherein the first length of the shaft body is about 711 mm to 813 mm.
 6. The billiard cue shaft of claim 5, wherein the first length of the shaft body is about 737 mm.
 7. The billiard cue shaft of claim 6, wherein the second length of the straight section of the shaft body is about 394 mm.
 8. The billiard cue shaft of claim 7, wherein the predetermined depth of the bore of the wooden rod is about 370 mm.
 9. The billiard cue shaft of claim 5, wherein the first outer diameter of the straight section of the shaft body is about 10.5 mm to 13.5 mm.
 10. The billiard cue shaft of claim 9, wherein the inner diameter of the bore 32 is about 5.36 mm to 10.94 mm.
 11. The billiard cue shaft of claim 9, wherein the first outer diameter of the straight section of the shaft body is about 12.75 mm.
 12. The billiard cue shaft of claim 11, wherein the predetermined inner diameter of the bore of the wooden rod is about 8.50 mm.
 13. The billiard cue shaft of claim 9, wherein the thickness of the outer layer is about 3.6% to 5.8% of the first outer diameter of the straight section of the shaft body.
 14. The billiard cue shaft of claim 13, wherein the thickness of the outer layer is about 0.74 mm.
 15. The billiard cue shaft of claim 5, wherein the weight of the shaft is about 96 grams to 120 grams.
 16. The billiard cue shaft of claim 15, wherein the weight of the shaft is about 106 grams. 